Effect Of Compound Probiotics On Milk Performance And Rumen Flora Of Mid-Lactation Dairy Cows

Probiotics increase milk yield and improve milk quality through regulating rumen fermentation,which in turn increase farmers’ income.Probiotics,treated as a natural and safety feed additives,have been widely used in dairy industry.Researches have suggested that compound probiotics are much better than single probiotics in improving milk yield,but less study explored the mechanism of compound probiotics enhanced milk yield,which dramatically limited the application of probiotics.This study explored the effect of compound probiotics on milk performance of mid-lactation dairy cows and the changes of rumen microbiota through high-throughput sequencing technology.Trial one:Effects of Compound Probiotics on Milk yield and Nutrients Digestibility of Dairy CowsTwenty healthy mid-lactation dairy cows,which were similar in milk yield(21.3±4.4 kg/d),days in milk(211±36.3 d)and parity(1.9±0.7),were randomly divided into two groups:control and treat,10 cows per group.The control group was fed with total mixed diet,and the treat group was supplied with extra 20 g compound probiotics per cow per day.Compound probiotics are consisted of Bacillus subtilis(≥2.0×109 CFU/g),Bacillus licheniformis(≥1.0×109 CFU/g)and Aspergillus oryzae(≥2.0×104 CFU/g).The cows were fed for 45 days,with 7 extra days for feed adaptation.The results showed that milk yield,milk protein and total solids yield were greater in treat group(P<0.05),with no difference in dry matter intake between treat and control group.The apparent digestibility of crude protein and Microbial protein yield were greater in treat group(P<0.05),with no difference in ruminal pH,ammonia and volatile fatty acids concentrations between the two groups(P>0.05).The profit of treat group was increased 14.6%compared with control group.Thus,compound probiotics can improve the rumen fermentation of mid-lactation dairy cows,increase nutrients apparent digestibility,and in turn improve milk yield and quality.Trial two:Effect of Compound Probiotics on Rumen Flora of Dairy CowsThis study explored the effects of compound probiotics on rumen flora.Eight dairy cows from each group in Trial 1 were allocated to collect rumen fluids samples to detect the relative abundance of rumen bacteria and archaea through high-throughput sequencing.(1)Effect of Compound Probiotics on Rumen Bacteria FloraAlpha diversity analysis indicated that compound probiotics had no influence on the ruminal bacterial flora diversity(P>0.05).At the phylum level,there is no significant difference was observed between the two groups(P>0.05).At the genus level,relative abundance of Ruminococcus was increased in treat group(0.05<P<0.10),and relative abundances of Succiniclasticum and Succinivibrio were significantly increased and decreased(P<0.05).(2)Effect of Compound Probiotics on Rumen Archaea FloraAlpha diversity analysis suggested that compound probiotics had no influence on rumen archaea flora diversity(P>0.05)and relative abundance of ruminal archaea at the levels of phylum and genus(P>0.05).In summary,compound probiotics improved rumen fermentation and promote propionate production,especially increased the relative abundance of Succiniclasticum.At the same time,compound probiotics increased the crude protein apparent digestibility,and then improved milk yield and quality,eventually improved the economic benefits.